Oil on spark plug
Car started to get shaky so I replaced all spark
plugs, number 6 was the worst, after replacing all
the plugs it continued to shake I pulled the all out
and once again number 6 plug had oil on it
One mechanic told me that the cat converter was
clogged and was causing pressure on the last
cylinder hens the oil
Another one said it was a faulty valve seal
Never heard of a cat causing oil to be pushed on the plugs, But Yes either valve seals or rings. You can do a compression wet test to determine which one it is. Never the less you are in for some repair.
if it is the cat it would cause pressure on all the cylinders not just one. it sounds to me more like a stuck valve
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